In the past, piezoelectric elements have been clamped to fuel lines in an effort to detect the surge of fuel through those lines, but accurate and reliable results have not been produced. One problem which has not been recognized and dealt with is that the signal developed has been relatively low in relation to the ambient noise on the line resulting from the vibration of the engine. A piezoelectric transducer has also been applied to an end fitting of a fuel line to detect the tendency of the fuel line to separate from the pump at one end, or from the nozzle at the other end, during fuel surges within the line. Such a system is disclosed in the Dooley et al. U.S. Pat. No. 4,109,518. To utilize these piezoelectric transducers, it has been necessary to disconnect the end fitting, at least momentarily, during the application of the transducer to the engine, thereby creating a potential for contamination of the fuel and/or leakage.